1. Field of the Invention
This invention relates to the field of spectroscopy and more particularly to apparatus for detecting and quantitatively measuring gaseous constituents through simultaneous transmission of their periodic spectra.
2. Description of the Prior Art
In apparatus used for spectroscopic gas analysis, light produced by scattering in gas is collected and transmitted to an interferometer scanned to transmit selectively and simultaneously the rotational Raman spectra of a preselected constituent of the gas. The output of the interferometer is converted to a detectable signal and displayed.
One of the major problems with such apparatus is the difficulty of analyzing quantities of gaseous constituents present in the low parts per million range. The output signal from the interferometer represents a relatively low intensity signal that is frequently altered or obscured by spectral interference between rotational Raman spectra of the gaseous constituent being analyzed and spectra of coexistent interfering gases. The problem is particularly troublesome when the gaseous constituent being analyzed is located at a point distant from the apparatus. To alleviate such problems it has been necessary to provide the apparatus with highly sensitive forms and combinations of detectors, sources, filteres, control systems and the like, which are relatively expensive.